Wait

 <!--
     After about 1 second, the text will change from 'Loading...' to 'Ready!'
 -->
 <h1 id="status">Loading...</h1>
 <script>
     (function () {
         setTimeout(function () {
             document.getElementById('status').textContent = 'Ready!'
         }, 1000);
     })();
 </script>

 import { Target } from '@serenity-js/protractor';
 import { by } from 'protractor';

 class App {
     static status = Target.the('status widget')
         .located(by.id('status'));
 }

 import { actorCalled, Duration } from '@serenity-js/core';
 import { BrowseTheWeb, Wait } from '@serenity-js/protractor';
 import { Ensure, equals } from '@serenity-js/assertions';
 import { protractor } from 'protractor';

 actorCalled('Aurora')
     .whoCan(BrowseTheWeb.using(protractor.browser))
     .attemptsTo(
         Wait.for(Duration.ofSeconds(1.5)),
         Ensure.that(App.status, equals('Ready!')),
     );

 // Please note that while the above implementation works,
 // this approach is inefficient because at best
 // the actor might wait too long and at worst the test
 // might become "flaky" if any external interference
 // (like network glitches, animations taking a bit too long etc.)
 // makes the actor wait not long enough.

 import { actorCalled } from '@serenity-js/core';
 import { BrowseTheWeb, Wait, Text } from '@serenity-js/protractor';
 import { equals } from '@serenity-js/assertions';
 import { protractor } from 'protractor';

 actorCalled('Aurora')
     .whoCan(BrowseTheWeb.using(protractor.browser))
     .attemptsTo(
         Wait.until(Text.of(App.status), equals('Ready!')),
         // app is ready, proceed with the scenario
     );

 // Wait.until makes the Actor keep asking a Question,
 // in this case Text.of(App.status), until the answer meets
 // the expectation, or a timeout expires (default: 5s).
 //
 // Please note that both Ensure and Wait can be used with
 // the same expectations, like `equals`.

 import { actorCalled, Duration } from '@serenity-js/core';
 import { BrowseTheWeb, Wait, Text } from '@serenity-js/protractor';
 import { equals } from '@serenity-js/assertions';
 import { protractor } from 'protractor';

 actorCalled('Aurora')
     .whoCan(BrowseTheWeb.using(protractor.browser))
     .attemptsTo(
         Wait.upTo(Duration.ofSeconds(3))
             .until(Text.of(App.status), equals('Ready!')),
         // app is ready, proceed with the scenario
     );